The present invention relates to the monitoring of mixtures, and in particular to real time monitoring using X-ray scanning. It has application in a number of fields where the monitoring and imaging of mixtures is required, and is particularly applicable to the measurement of the flow rates of the different fractions in moving mixtures of fluids, such as the measurement of oil flow from oil wells. It is also applicable to slurry flow monitoring and measurement, the monitoring of fluidization processes, and in the monitoring of mixing processes.
Typically, an oil well is one of a number of wells that collectively form an oil field. As well as extracting oil, water and gas from an individual oil well, it is sometimes necessary to recycle water down an oil well back into the ground. Typically, this pumped water is used to facilitate diffusion of oil through the porous rocks in the ground towards a well (or wells) for subsequent collection. By careful design of pumping and extraction rates, it is possible to maximise the yield of oil from the field.
Often, the output from several extracting oil wells are joined into a single pipeline for subsequent downstream processing. To optimise the production process, it is necessary to know the fraction of oil and water in the liquid phase and also to know the volumes of oil and water produced by each well in the field. By combining this information with an understanding of the geophysics and seismology data of the field itself, it is believed to be possible to improve on the quantity of oil produced from the field and to reduce the cost of production. Such measurements of oil and water phase fraction and velocity require instrumentation to be placed at the well head.
Known instrumentation for this purpose relies on measurement of linear attenuation coefficient of the flow using a dual-energy gamma measurement once the flow has been homogenised by use of a mechanical system. A second known approach is to measure electrical properties of the fluid (including permittivity and conductivity) and from this to infer phase fraction of oil and water.